WAXD and FTIR Studies of Electron Beam Irradiated Biodegradable Polymers

Poly（L-lactic acid） （PLLA） and poly（e-caprolactone） （PCL） have been receiving much attention lately due to their biodegradability in human body as well as in the soil, also due to their biocompatibility, environmentally friendly characteristics and non-toxicity. Morphology of biodegradable polymers affects the rate of their biodegradation. A polymer that has high degree of crystallinity will degrade at a slower rate due to the inherent increased stability. PCL homopolymer crosslinking degree increases with increasing doses of high energy radiation. On the other hand, the irradiation ofPLLA homopolymer promotes mainly chain-scissions at doses below 250 kGy. In the present work, twin screw extruded films of PLLA and PCL biodegradable homopolymers and 50：50 （w：w） blend were electron beam irradiated using electron beam accelerator Dynamitron （E = 1.5 MeV） from Radiation Dynamics, Inc. at doses in the range of 50 kGy to 103 kGy in order to evaluate the effect of electron beam radiation. Wide-angle X-ray diffraction （WAXD） patterns of non irradiated and irradiated samples were obtained using a diffractometer Rigaku Denki Co. Ltd., Multiflex model; and Fourier transform infrared spectroscopy （FTIR） spectra was obtained using a NICOLET 4700, attenuated total reflectance （ATR） technique. By WAXD patterns of as extruded non irradiated and irradiated PLLA it was verified broad diffusion peaks corresponding to amorphous polymer. There was a slight increase of the mean crystallite size of PCL homopolymer with increasing radiation dose. PCL crystalline index （CI） decreased with radiation dose above 500 kGy. But then, PLLA CI increased with radiation dose above 750 kGy. From another point of view, PLLA presence on the 50：50 blend did not interfere on the observed mean crystallite size increase up to 250 kGy. From 500 kGy to 103 kGy the crystallite size of PCL was a little bigger in the blend than the homopolymer. In contrast, FTIR results have shown that this technique was not sensitive enough to observe the degradation promoted by ionizing radiation of the studied homopolymers and blends, and neither on the miscibility of the blends.

Synthesis, Structural Studies and Reactivity of Two cis-Bis（phosphine）bis（silyl） Palladium（ll） Complexes

Treatment of 1,2-C6H4（SiH3）（SiH3） （1） or 1,2-C6H4（SiMe2H）（SiH3） （2） with Pd（dcpe）（PEt3）2 （dcpe？=？Cy2PCH2CH2PCy2） in the ratio of 1∶1 affords two cis- bis（silyl） palladium（II） complexes {1,2-C6H4（SiH2）（SiH2）}PdII（dcpe） （3） and {1,2- C6H4（SiMe2）（SiH2）}PdII（dcpe） （4） with good thermal stability respectively. To the best of our knowledge, only ten silyl palladium complexes prepared from these two chelating hydrosilane ligands are presented in the Cambridge Structural Database. The structures of complexes 3 and 4 are unambiguously determined by single crystal X-ray analysis and multinuclear NMR spectroscopic studies.

Synthesis, Structural Characterization and Reactivity of a Bis（phosphine）（silyl） Platinum（ll） Complex

Treatment of 1,2-C6H4（SiH3）（SiH3） （1） with Pt（dmpe）（PEt3）2 （dmpe=Me2PCHeCH2PMe2） in the ratio of 1 ： 1 leads to the complex {1,2-C6H4（SiH2）（SiH2）}PtH （dmpe） （2）, which can react with proton organic reagent bearing hydroxy group with low steric hindrance to form a tetra-alkoxy substituted silyl platinum（II） compound （3）. Com- pounds 2 and 3 are the very rare examples of silyl transition-metal complexes derived from this chelating hydrosi- lane ligand. To the best of our knowledge, there are only 6 examples of silyl metal complexes prepared from this ligand with such structural features registered in the Cambridge Structural Database, among them, only one silyl platinum（II） compound is presented. The structures of complexes 2 and 3 were unambiguously determined by mul- tinuclear NMR spectroscopic studies and single crystal X-ray analysis.